JPS6178222A - Detection circuit for digital pattern - Google Patents

Abstract

PURPOSE:To detect a similar pattern as well as identical pattern by using plural constant current circuits and analog synthesis circuits to compare an input digital code string and a reference digital code string quantitatively. CONSTITUTION:An input digital code string Din is inputted to a shift register 1. The shift register 1 compares the input digital code string Din with the reference digital code string (set by selecting a positive logical output +Q or a negative logical output -Q of each shift register), and the presence of coincidence is outputted in parallel at each bit. A coincidence signal generated at each unit code becomes a control signal of a switch array 2. Constant current sources Ic1-Ic8 are connected respectively to switches S1-S8 and opposite terminals are connected in common. Since a voltage in response to the coincidence of the input digital string and the reference digital string is obtained on a line 10, it is compared with a reference value by a comparator CP so as to detect a similar pattern in addition to a completely coincident pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a technique that is particularly effective when applied to digital signal processing technology and further to digital pattern detection.

[Background technology]

For example, in digital data communication or spread spectrum communication, a function to detect a specific pattern of digital code strings is required.

Conventional means for detecting this particular pattern of digital code strings include logically comparing an input digital code string taken out in parallel from a shift register or the like with a reference digital code string. According to this means, it is detected whether or not the digital pattern of the input digital code string matches the pattern of a predetermined reference digital code string.
Alternatively, it can be taken out as an O logic signal. In this case, the logical comparison operation can be performed in hardware or software using multiple AND gates or a microcomputer.

In addition, as an application example of the pattern detection circuit, for example, (
1) “Transistor Technology” published by CQ Publishing Company, June 1979
Monthly issue P211-213, (2) "Nikkei Electronics" published by Nikkei McGraw-Hill, July 30, 1984, p11
8 etc.

However, with this technique, what can be detected is whether or not the patterns of the input digital code string and the reference digital code string completely match, and it is not possible to detect, for example, a similar pattern that is partially different. If similar patterns are to be detected, a logic circuit is required to detect whether or not each similar pattern matches.

However, the number of combinations of similar patterns is very large. For example, if you try to detect a digital code string of a specific pattern consisting of 16 bits including similar patterns that differ by up to 2 bits, 16C2=I6XI5/lX
2=120 logical comparisons would have to be made. Furthermore, if we extend the similarity range to 3 bits, we get
The number of combinations increases further, and 560 logical comparisons must be performed.

As described in 1- above, conventional digital signal processing means are relatively good at detecting whether or not there is a complete match. It was very difficult to detect or judge ambiguous content. The inventors have found that while this is an advantage of conventional digital signal processing means, it is also a disadvantage.

[Purpose of the invention]

An object of the present invention is to provide a digital pattern detection technique that can easily and quantitatively detect ambiguous contents, which are difficult to detect with conventional digital signal processing means.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the l and O signals corresponding to the coincidence of each qt place code of the input digital code string and the reference digital code string are generated for each qt1 code, and each 11 is generated for each qt place code. By adding analog signals of 0 and 0 to each other, it is possible to detect not only completely matching target patterns but also similar patterns, and this detection can also be carried out quantitatively. It accomplishes its purpose.

(Embodiments) Hereinafter, typical embodiments of the present invention will be described with reference to the drawings.

In the drawings, the same reference numerals indicate the same or corresponding parts.

First, the digital pattern detection circuit of the embodiment shown below is a digital pattern detection circuit that detects a digital code string of a specific pattern, and detects whether or not each unit code of an input digital code string and a reference digital code string matches each other. Corresponding 1 and O signals are generated for each unit code. At the same time, the 1 and 0 signals generated for each unit code are added together in analog form. Then, from the result of this addition, an analog signal having a magnitude corresponding to the mutual similarity between each pattern of the input digital code string and the reference digital code string is obtained. Here, the 2-bit qt code is composed of 1-bit digital data.

FIG. 1 shows a specific embodiment of the digital pattern detection circuit described above.

The digital pattern detection circuit shown in the figure includes a shift register 1, a switch row 2, a constant current circuit row 3, a load resistor Ro,
and a comparison circuit CP.

The shift register 1 has a number of shift 1 to stages F1 to F corresponding to the number of bits constituting the digital code string 1 to be detected.
It has 8. The input digital code string Din is sequentially shifted bit by bit through each shift stage F1 to F8 in synchronization with a clock pulse CP. Each shift stage F1
The data held in ~F8 is output in parallel, one bit at a time, as a positive logic output +Q or a negative logic output -Q.

The switch row 2 has a number of switches 81 to S8 corresponding to the shift stages F1 to F8. Each switch 5l-3R
is MO8Wi field effect transistor or bipolar 1
-Each consists of active elements such as transistors. The opening and closing operations of each of the switches 81 to S8 are performed by the positive logic output +Q or the negative logic output -Q of the shift stage F1 to F8 at the corresponding position.

The constant current circuit array 3 includes constant current circuits Icl to Tc8, the number of which corresponds to the switches 81 to S8.

Each of the constant current circuits Tcl to Tc8 is configured to flow the same constant current i. Each constant current circuit Tcl to Ic8
are commonly connected to each other via switches 81 to S8 at corresponding positions, and this common connection point is further connected to the power supply Vcc via a load resistor RO in series.

The comparator circuit cp compares the voltage Vo appearing across the load resistor Ro with the reference voltage Vs, and when Vo > Vs, its output becomes active and becomes a digital detection output D.
It is designed to output O.

Next, the operation will be explained.

First, the bit pattern of the reference digital code string is, for example, r
Suppose that it is set to lolololoJ. In this case, each shift stage F
The connections are such that the positive logic output +Q or the negative logic output -Q of each of the switches 1 to F8 drives all the switches 81 to S8 to close. That is, the pattern of the reference digital string is set by selecting the positive logic output +Q or the negative logic output -Q output for each of the shift stages F1 to F8.

Here, when the pattern of the input digital code string input to the shift register 1 is exactly the same as that of the reference digital code string, all the switches 81 in the switch string 2
~S8 is closed. As a result, the sum Σ1=81 of the constant currents i flowing through all the constant current circuits Icl to Ic8 in the constant current circuit array 3 flows through the load resistor Ro. At this time, a detected output voltage Vo of Vo:=8 i Ro is obtained from both ends of the resistor Ro.

Furthermore, when the pattern of the input digital code string Din input to the shift register l is a similar pattern that differs by one bit from that of the reference digital code string, no matter how different the pattern is, any one of the switch strings in the switch string 2 1
Only one switch is open and the remaining seven switches are closed. As a result, the current flowing through the load resistor Ro becomes 71, which is less than before by i. At this time, a detected output voltage Vo of Vo=7iRo is applied from both ends of the resistor Ro.
is obtained.

Furthermore, when the pattern of the input digital code string Din input to the shift register l is a similar pattern that differs from that of the reference digital code string by 2 bits, in this case as well, whatever the difference, the Only any two switches are open, and the remaining six switches are closed. As a result, the load resistance Ro
The current flowing through is 61, which is even less than before by i.

A detection power voltage vO of Vo=6 iRo is obtained from both ends of the resistor Ro.

As described above, the detected output voltage vO changes depending on the magnitude of the mutual difference between the patterns of the input digital code string Din and the reference digital code string.

The detected output voltage vO takes the maximum value Vo=8 i Ro when both patterns completely match, and decreases by iRo each time the difference between the two patterns increases by 1 bit.

FIG. 2 is a graph showing the relationship between the pattern similarity between the input digital code string and the reference digital code string and the above-mentioned test voltage Vo.

As described above, the pattern similarity between the input digital code string and the reference digital code string is quantitatively detected as the detected output voltage Vo. Therefore, in the case of the embodiment shown in FIG. 1, the similar range of detected patterns can be freely selected by simply selecting the reference voltage Vs of the comparator circuit CP. For example, the reference voltage Vs is set to 8jR.
By setting o>Vs>7iRo, only perfectly matching identical patterns can be detected. In addition, the reference voltage V
If s is set to 7 iRo>Vs>6 iRo, it is possible to detect similar patterns that differ by only one bit. Furthermore, the reference voltage Vs is 6 i Ro>Vs>
When set to 5 i Ro, similar patterns that differ by up to 2 bits can be detected. Furthermore,
The above reference voltage Vs is 4 i Ro>V s>3 i R
If set to o, it is also possible to detect whether or not the matching number of pins 1- is in the majority, or to perform so-called majority logic.

Furthermore, if an A/D converter is used in place of the comparison logic CP described in 1., a signal quantitatively indicating the pattern similarity between the input digital code string and the reference digital code string can be obtained as digital data. Become.

As described above, processing of contents including ambiguous elements, which conventional digital signal processing means are not good at, can be performed by hardware using very simple and concise means. As a result, in digital data communications or spread spectrum communications, for example, it is possible to detect not only complete patterns but also approximate patterns that are partially destroyed or partially lost, so weak synchronization signals hidden in noise can be detected. be able to be detected. In other words, synchronization detection that is resistant to disturbances can be performed.

Furthermore, in the field of information processing using computers, it can be very effective, for example, in determining the similarity of word trademarks and classifying and organizing them. Furthermore, data containing ambiguous elements can be easily and concisely processed using hardware rather than software, making it possible to efficiently process intellectual problems that involve advanced content, such as reasoning. become able to.

FIG. 3 shows an alternative embodiment of the portion of the circuit shown in FIG.

In the embodiment shown in the figure, the switches 81 to S8 and the constant current circuits Icl to Ic8 are configured by integrated injection logic iIL. Q
p + Q n indicates a bipolar transistor forming the ITL. By connecting a part of the output of this ITL to the input side, a constant current circuit using a current mirror circuit...T
c3. Ic4... is configured. The operation of each constant current circuit is controlled by a logic signal input to the base of transistor Qp. Thus, by using ITL.

The switch row 2 and the constant current circuit row 3 can be configured very easily.

〔effect〕

(1) Generate 1 and O signals for each unit code corresponding to the presence or absence of a match between each unit code of the input digital code string and the reference digital code string, and also generate 1 and 0 signals for each unit code. By adding the signals in analog form to each other, it is possible to detect not only a completely matching target pattern but also similar patterns, and the detection can be carried out quantitatively.

Although the invention made by the present inventor has been specifically explained above based on examples, it goes without saying that this invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof. Nor. For example, the input digital code string may be data input in parallel.

[Application field]

The above explanation has mainly been about the case where the invention made by the present inventor is applied to bit pattern detection technology in digital data communication or spread spectrum communication, which is the field of application that formed the background of the invention.
The present invention is not limited to this, and can be applied, for example, to pattern detection techniques for more complex code strings in which codes made up of multiple bits are assembled as minimum units.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the digital pattern detection circuit according to the present invention, FIG. 2 is a characteristic diagram showing the operation of the circuit shown in FIG. 1, and FIG. 3 is a circuit diagram showing the operation of the circuit shown in FIG. 1. FIG. 6 is a circuit diagram showing another embodiment of a portion. 1...Shift register, F1-F8...Shift stage,
+Q, -Q...Holding logic output of each shift stage, 2...
Switch row, S1 to S8... Switch, 3... Constant current circuit row, Tcl to Ic8... Constant current circuit, Ro...
- Load resistance, cp... Comparison circuit, Vs... Reference voltage, Vo... Analog detection output voltage, Do... Digital detection output, ITL... Integrated injection logic.

Claims (1)

[Claims] 1. A digital pattern detection circuit that detects a digital code string of a specific pattern, which detects 1 and 0 corresponding to the presence or absence of a match between each unit code of an input digital code string and a reference digital code string. A signal is generated for each unit code, and the 1 and 0 signals generated for each unit code are added together in analog form, and from the result of this addition, the interaction between each pattern of the input digital code string and the reference digital code string is determined. A digital pattern detection circuit is characterized in that it obtains an analog signal of a size according to the degree of similarity between the two. 2. The digital pattern detection circuit according to claim 1, wherein the digital code string uses 1-bit digital data as a unit code.